Method of making an image intensifier array and resultant article



Jan. 27, 1970 SMITH ET AL 3,492,523

" METHOD OF MAKING 'AN IMAGE INTENSIFIER ARRAY AND RESULTANT ARTICLEOriginal Filed June 9, 1961 GUIDE PI'NS STACKS OF ETCHED SHEETS BAGDASARDERADOORIAN I HAYDEN M. SMITH w BY ROBERT R. THOMPSON ATTORNEY UnitedStates Patent US. Cl. 313-105 9 Claims ABSTRACT OF THE DISCLOSURE Thisinvention pertains to a method of manufacturing an image intensifierarray and the resultant article. A plurality of thin glass sheetscompounded with oxides of lead and bismuth, are perforated as byphotoetching, the glass sheets are stacked so that the perforationsbecome aligned to form individual channels, and the individual thinsheets are bonded together with sufiicient sheets being used toestablish the desired length of the channel. The interior surfaces ofthe array channels are then hydrogen reduced by heating said sheets toan elevated temperature while flowing hydrogen through the passages toproduce a secondary emissive resistive surface.

BACKGROUND AND SUMMARY OF THE DEVELOPMENT This is a continuation of ourcopending application Ser. N0. 405,020, filed October 14, 1964, which isa continuation of application Ser. No. 116,044, filed June 9, 1961, andentitled Image Intensifier Array, both now abandoned.

In the Goodrich and Wiley patent, an image intensifier or channelmultiplier is disclosed wherein a tube or channel of relatively smalldiameter in the order of .001 inch is provided on the inside surfacewith a secondary emissive resistive material. A voltage differential isplaced across the tube or channel to accelerate incoming electronsthrough the channel and also provide current in the resistive coatingfor supplying electrons that are used in the secondary emission. Anarray of many of these tubes may be placed together to form a large areaelectron multiplier. An image intensifier can be made by placing aphotocathode at one end of the array for conventing light rays intocorresponding electron emission, and providing a phosphor screen at theother end of the array to convert the multiplied electrons into visibleradiation.

This invention provides a method for constructing an array of suchmultipliers disclosed in the Goodrich and Wiley patent. In thisinvention a plurality of thin glass sheets compounded with oxides oflead and bismuth, are perforated as by photoetching, the glass sheetsare stacked so that the perforations become aligned to form individualchannels, and then the individual thin sheets are bonded together withsufficient sheets being used to establish the desired length of thechannel.

It is therefore an object of this invention to form an array of smalldiameter individual tubes or channels which have a secondary emissiveresistive surface on the interior thereof, which comprises the steps ofperforating a plurality of thin glass sheets which contain compounds tomake the sheets conductive to a desired degree, and stracking andbonding a sutficient number of sheets together with the perforationsaligned to form a plurality of individual small diameter channels. Theinterior surfaces of the array channels are then hydrogen reduced3,492,523 Patented Jan. 27, 1970 or otherwise treated to provide thedesired resistive characteristics.

It is a further object of this invention to provide in such method thestep of photoetching to produce the perforations in the individual glassplates.

It is a further object to place near the end of the array, such asbetween the final two layers of glass sheets, a highly conductiveperforated plate so that a voltage lead may be attached to the plate toprovide a gate for electrons formed in and coming through individualchannels.

These and other objects and advantages will become more apparent when apreferred embodiment of this invention is considered in connection withthe drawings in which:

FIGURE 1 is a plan view of a single sheet having a plurality of holesformed therein;

FIGURE 2 is a view in perspective of a partially completed stack ofindividual glass plates which are perforated and cemented in accordancewith this invention; and

FIGURE 3 is a perspective view of a completed array.

Shown in FIGURE 1 is a glass sheet or film 20 which is in the order of.005 inch in thickness and may be composed of a mixture of 32 percentlead oxide, 61.3 percent silicon dioxide, 6.2 percent of bariumcarbonate and .5 of 1 percent bismuth trioxide. A plurality of holes 22are formed in the sheet with the holes being small in diameter, in theneighborhood of .001 inch, and closely spaced. The spacing between holesin this embodiment is .1 the diameter of a hole. Two guide slots 24, 26are formed near diagonally opposite corners of the sheet to effectalignment of the sheets as later explained.

The holes or perforations 22 may be formed in sheet 20 by a processknown as photoetching. In this process a coating which is sensitive tolight is placed on sheet 20.

. A transparent or transulcent negative having a plurality of opaqueareas corresponding to the size and placement of holes 22 desired insheet 20, is placed over the light sensitive coating and is exposed to alight for a predetermined length of time. The negative is removed andcoating is then developed in a solution which dissolves the areas notsubjected to the light, which would be the areas under the opaquesections corresponding to holes 22. An etch is used on the surface ofthe coating, which now has holes through it corresponding to holes 22 inglass sheet 20, to etch holes in sheet 20. After the etching iscomplete, a dissolver for the coating is utilized to clean the coatingfrom sheet 20. This process is well known in the art and specificmaterial for the light sensi tive coating, developing solution and etchcan be obtained by consulting Techniques for Ruling and Etching PreciseScales in Glass and their Reproduction by Photoetching with a New LightSensitive Resist US. National Bureau of Standards, circular 565:1-36, p.30 C, Superintendent of Documents 1955. Also, photosensitive glass maybe used in which case the step of applying and removing the resistcoating on the glass becomes unnecessary.

Next, the individual glass sheets 20, prepared as previously describedwith perforations or holes 22, are stacked so that guide slots 24, 26are aligned, and the stack is placed over guide pins 28, 30, FIGURE 2,so that the slots 24, 26 register with the slide over pins 28 and 30. Inthis manner all of the perforations or holes 22 become aligned to formthe desired channels or tubes. After each sheet is placed over guidepins 28 and 30, a cement such as Coming Glass Company Pyroceram number89 or solder glass may be applied to the outer boundaries thereof, tocement together adjacent sheets 20 upon the application of heatsufiicient to fuse the cement or solder glass but not hot enough to meltthe sheets 20. Of course, the sheets may be fastened together in othersuitable ways. Near one or both ends of the array, one or moreconductive sheets 32, may be placed between two of the glass sheets 20.Sheets 32 may be of a metallic material such as a thin aluminum film andmay have the holes formed therein in a manner similar to the glasssheets 20. A voltage lead 34 may be connected to the conductive sheetand a voltage applied to provide a gate to prevent the flow ofelectrons. For example, if a high negative potential is applied to theconductive sheet 32, the flow of electrons will be inhibited.

After the stack or array is completed and the individual sheets arecemented to each other or to conductive sheets, the array is subjectedto a reducing procedure. Such reduction can be done by heating the arrayto 325 to 500 degrees centigrade for 8 to 16 hours while flowing oneliter per minute of pure hydrogen through the channels of the array.This will provide a resistive surface of the desired characteristics fora particular application of about 100 angstroms units thick.

A conductive coating 36 may be put on the sheet at each of the arraywith a conductive paint such asa gold or silver paint or by vapordepositing the gold or silver or other conductive material at a steepangle on the sheet ends so that the conductive coating will not form onmore than a minimum of the tube or channel interiors.

When this is completed, leads 38, 40 are attached to the conductivecoatings and a voltage source 42 is placed therebetween to provide thenecessary accelerating field across each tube and provide current forsecondary emission form the resistive surfaces on each tube or channel.

Although this invention has been disclosed and illustrated withreference to particular applications, the principles involved aresusceptible of numerous other applications which will be apparent topersons skilled in the art. The invention is, therefore, to be limitedonly as indicated by the scope of the appended claims.

What is claimed is:

1. A method of making an image intensifier array comprising the steps offorming in a plurality of thin insulative glass sheets containing atleast one of the elements lead and bismuth, a plurality of relativelysmall diameter holes which are spaced apart a distance which is only afraction of said hole diameters, stacking a plurality of insulativesheets so that each of said insulative sheets is in direct contact withanother insulative sheet, aligning the holes of each sheet with theholes in adjacent sheets thereby forming a plurality of tubular passageswith the number of said sheets in stacked relation being suflicientlylarge so that the length to diameter ratio of said tubular passages isrelatively large, bonding and sheets together, hydrogen reducing thetubular passages formed in said sheets by heating said sheets to anelevated temperature while flowing hydrogen through the passages toproduce a secondary emissive resistive surface on the side of saidtubular passages.

2. A method of making an image intensifier array comprising the steps offorming in a plurality of thin insulative sheets which are in the orderof .550" in thickness a plu-' rality of relatively small diameter holeswhich are in the order of .001 in diameter and spaced apart a distancewhich is only a fraction of said hole diameters, stacking a plurality ofinsulative sheets so that each of said insulative sheets is in directcontact with another insulative sheet, aligning the holes of each sheetwith the holes in adjacent sheets thereby forming a plurality of tubularpassages, bonding said sheets together, hydrogen reducing the tubularpassages formed in said sheets by heating said sheets to an elevatedtemperature while flowing hydrogen through the passages to produce asecondary emissive resistive surface, placing a conductive coating onthe faces of the sheet at each end of the array, and establishing anaccelerating field across each tubular passage and providing current forsecondary emission from the surface of the tubular passages by applyinga voltage between the conductive coatings.

3. A method of making an image intensifier array comprising the steps offorming in each of a plurality of thin insulative sheets a plurality ofrelatively small diameter holes which are spaced apart a distance whichis only a fraction of said hole diameters, stacking a plurality ofinsulative sheets so that each of said insulative sheets is in directcontact with another insulative sheet, said sheets being formed of glasscontaining one of the elements lead or bismuth, aligning the holes ofeach sheet with the holes of adjacent sheets thereby forming a pluralityof tubular passages with the number of said sheets in stacked relationbeing sufliciently large so that the length to diameter ratio of saidtubular passages is relatively large, bonding said sheets together,hydrogen reducing the tubular passages formed in said sheets by heatingsaid sheets to an elevated temperature while flowing hydrogen throughthe passages to produce a secondary emissive resistive surface, applyinga conductive coating on the faces of the sheet at each end of the array,and establishiing an accelerating field across each tubular passage andproviding current for secondry emission for the surface of the tubularpassages by applying a voltage between the conductive coatings.

4. The method of claim 3 further including the step of forming guideslots in each of the sheets, and each of said stacking and aligningsteps including the substep of aligning said slots of guide pins.

5. The method of claim 3 in which said bonding step is performed byapplying a cementing medium to the outer boundaries of the sheets andfusing the cementing medium in place.

6. The method of claim 3 further including the steps of placing aconductive layer between two of the insulative sheets, connecting avoltage lead to the conductive layer, and applying a voltage to thevoltage lead to gate the flow of electrons through said tubularpassages.

7. The method of claim 1 wherein said elevated temperature is within therange of approximately 325 to 500 C.

8. The product fabricated from the method of claim 1.

9. The product fabricated from the method of claim 2.

References Cited UNITED STATES PATENTS 2,588,920 3/1952 Green. 2,597,5625/1962 Blodgett.

2,777,084 1/1957 Laiferty.

2,806,958 9/1957 Zunick.

2,817,781 12/1957 Sheldon 3l3-l05XR 2,821,637 l/l958 Roberts etal.

3,062,926 11/1957 McGee 313 355 XR 3,128,408 4/1960 Goodrich etal.

ROBERT F. BURNETT, Primary Examiner R. L. MAY, Assistant Examiner US.01. X.R.

UNITED S'IA'IES PATENT OFFICE CERTIFICATE OF CORRECTION mom No.3,422,523 Dated anuary 27, 1 70 lnv( ntor(.-;) I lq yt le r l IilSm1'th, Robert R. Thompson, Bagdasar Deradoor'ian It is (:crt'Ifiml lhaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

IN THE SPECIFICATION Column l line 50, conventing. should read-converting-.

Column l line 69, stracki ng. should read --stack1'ng--.

Column 2, line 64, the. should read -and-.

Column 3, line 23, --end-- should appear after .each.

Column 3, line 32, .form. should read "from".

IN THE CLAIMS Claim 1 column 3, l ine 52, and. should read --sa1d-.

aim-21) All, when Nov 1 0 (SEAL) Attest:

Admin Offioer vmmm E. saw

g oomissioner or Pam FORM P0-1050 [10-69) USCOMM-DC GOING-P09 w u s.oovnnncm nmmna OFFICE: an o-su-su

